Multi-layer pipe manufacturing apparatus and method of manufacturing multi-layer pipes using the same

ABSTRACT

An apparatus for manufacturing a multi-layer pipe is provided. The apparatus includes a ram extruding a matrix pipe, which is formed by inserting one or more insert pipes having different diameters into a receiving pipe, with a constant compression force, a heat-treatment unit heat-treating the matrix pipe extruded from the ram, and a drawing unit drawing, with a constant drawing force, the matrix pipe passing through the heat-treatment unit into a multi-layer pipe having a predefined diameter.

TECHNICAL FIELD

The present invention relates generally to a multi-layer pipemanufacturing apparatus and a method of manufacturing a multi-layer pipeusing the same. More particularly, the present invention relates to anapparatus for simultaneously bonding a plurality of pipes bothmechanically and metallurgically with relatively simple configurationand process to economically manufacture a multi-layer pipe, and a methodof manufacturing the multi-layer pipe using the same.

BACKGROUND ART

Generally, a multi-layer steel pipe including a double-layer steel pipeis manufactured with an adhesive or thermal bonding using a differencein thermal expansion coefficients.

Recently, such a multi-layer steel pipe has been manufactured usingmetallurgical bonding, mechanical bonding, and thermal bonding.

The mechanical bonding may use a hydraulic forming method, a stretchreducing mill (SRM) rolling method or the like, wherein the hydraulicforming method is a method that generates a bonding force using plasticdeformation of an inner pipe and recovered elasticity of an outer pipe,and the SRM rolling method is a method that realizes mechanical bondingused in manufacturing a seamless steel pipe.

Although the hydraulic forming method employs a hydro-forming methodwhere fluid such as gas, water or the like is supplied in the inner pipeso that the inner pipe is expanded with hydraulic pressure and is bondedonto the outer pipe, it has problems of a restricted length of aproduct, increased cost of preparing a die for each size for manufactureof a multi-layer pipe, and increased cost and time due to the complexprocess of supply, post-treatment or the like of working fluid.

Further, the SRM rolling method also has problems in thatmass-production equipment is needed in hot rolling using rolls, and aprocess of manufacturing a matrix pipe by inserting an inner pipe intoan outer pipe is not performed smoothly.

DISCLOSURE Technical Problem

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the related art, and the present inventionis intended to propose an apparatus for simultaneously bonding aplurality of pipes both mechanically and metallurgically with arelatively simple configuration and process to economically manufacturea multi-layer pipe, and a method of manufacturing the multi-layer pipeusing the same.

Technical Solution

In order to achieve the above object, according to one aspect of thepresent invention, there is provided an apparatus for manufacturing amulti-layer pipe. The apparatus includes: a ram extruding a matrix pipe,which is formed by inserting one or more insert pipes having differentdiameters into a receiving pipe, with a constant compression force; aheat-treatment unit heat-treating the matrix pipe extruded from the ram;and a drawing unit drawing, with a constant drawing force, the matrixpipe passing through the heat-treatment unit into a multi-layer pipehaving a predefined diameter.

The compression force and the drawing force may be identical ordifferent.

An outer surface of an outermost insert pipe inserted into the receivingpipe may come into contact with an inner surface of the receiving pipe,and an outer surface of another insert pipe inserted into aformer-inserted insert pipe inserted into the receiving pipe may comeinto contact with an inner surface of the former-inserted insert pipe.

The heat-treatment unit may be a heat furnace accommodating the matrixpipe extruded from the ram, or a high-frequency induction heaterarranged along a direction in which the matrix pipe extruded from theram is formed.

The high-frequency induction heater may include a single-frequencygenerator for high-frequency induction heating bonding of the receivingpipe and the insert pipes that are formed of the same material toconstitute the matrix pipe, and a multi-frequency generator forhigh-frequency induction heating bonding of the receiving pipe and theinsert pipes, respectively, that are respectively formed of differentmaterials to constitute the matrix pipe.

The matrix pipe may be heat-treated at a temperature ranging from 150°C. to 1350° C. by the heat furnace or the high-frequency inductionheater.

The drawing unit may include a die having an extrusion hole sectionthrough which the multi-layer pipe is extruded from the ram into asmaller outer diameter relative to that of the matrix pipe, a clampclamping an end of the multi-layer pipe extruded from the die, and acarrier carrying the multi-layer pipe with a constant drawing forcealong a direction of the multi-layer pipe being extruded, the clampbeing provided to the carrier.

The extrusion hole section may include a first end hole having a firstdiameter that is disposed on a first side of the die so as to face theram, a middle hole disposed in the die concentrically with the first endhole and having a second diameter smaller than the first diameter, asecond end hole disposed on a second side of the die opposite to thefirst side, concentrically with the middle hole and having the seconddiameter, a first extrusion guide part connecting the first end hole andthe middle hole and having a diameter decreasing towards the carrier,and a second extrusion guide part connecting the middle hole and thesecond end hole and having a constant diameter towards the carrier,wherein the first diameter corresponds to an outer diameter of thematrix pipe and the second diameter corresponds to an outer diameter ofthe multi-layer pipe.

The extrusion guide parts may be provided with a duplex physical vapordeposition (PVD) coating layer or a diamond-like-carbon (DLC) coatinglayer.

The drawing unit may further include a mandrel extending from thecarrier towards the ram separately from the clamp and disposed at thecenter of the clamp so as to, when inserted into the multi-layer pipe,maintain an inner diameter of the multi-layer pipe to be constant.

The mandrel may be provided, on an outer surface thereof, with a duplexphysical vapor deposition (PVD) coating layer or a diamond-like-carbon(DLC) coating layer.

The clamp may be provided with a plurality of chucks attached to thecarrier and radially arranged so as to be separated from or to contactan outer surface of the multi-layer pipe.

The receiving pipe and the insert pipes may be famed of the samematerial or different materials.

The receiving pipe and the insert pipes may be any one of an electricresistance welding (ERW) pipe and a seamless pipe.

The insertion pipe may be famed of one of stainless steel, aluminum,aluminum alloy, copper, copper alloy, nickel, nickel alloy, and acombination thereof.

The receiving pipe may be formed of one of carbon steel, cobalt-basealloy steel, aluminum, aluminum alloy, brass, high manganese steel, anda combination thereof.

The receiving pipe or the insert pipe may be provided, on an outer orinner surface thereof, with a plurality of reinforcing ribs spaced atregular intervals and linearly extending along a longitudinal directionof the receiving pipe or the insert pipe, the reinforcing ribs havingalternating linear ridges and valleys.

The receiving pipe or the insert pipe may be provided, on an outer orinner surface thereof, with a plurality of reinforcing ribs spaced atregular intervals and involutely extending along a longitudinaldirection of the receiving pipe or the insert pipe, the reinforcing ribshaving alternating involute ridges and valleys.

The apparatus may further include a rotary actuator provided in one orboth of the ram and the drawing unit and driven to rotate the extrudedmatrix pipe or the drawn multi-layer pipe in one direction.

In another aspect of the present invention, there is provided a methodof manufacturing a multi-layer pipe using an apparatus for manufacturinga multi-layer pipe, the method including: a first stage of forming amatrix pipe by inserting one or more insert pipes having differentdiameters into a receiving pipe; a second stage of introducing thematrix pipe into a ram to extrude the matrix pipe with a constantcompression or extrusion force; a third stage of introducing the matrixpipe extruded from the ram into a heat-treatment unit to heat-treat thematrix pipe; and a fourth stage of clamping an end of the matrix pipeheat-treated by the heat treatment unit and drawing the matrix pipe witha constant drawing force to form a multi-layer pipe having a desireddiameter, using a drawing unit.

An outer surface of an outermost insert pipe inserted into the receivingpipe may come into contact with an inner surface of the receiving pipe,and an outer surface of another insert pipe inserted into aformer-inserted insert pipe inserted into the receiving pipe may comeinto contact with an inner surface of the former-inserted insert pipe.

In the third stage, the matrix pipe extruded by the ram may beheat-treated at a temperature ranging from 150° C. to 1350° C. by a heatfurnace accommodating the matrix pipe or a high-frequency inductionheater arranged along a circumferential face of the matrix pipe.

Advantageous Effects

According to the above-mentioned configuration, the present inventionprovides the following effects.

With the configuration in which the matrix pipe is formed by insertingthe insert pipe(s) into the receiving pipe, the matrix pipe is extrudedwith a constant extrusion force by the ram, the matrix pipe isheat-treated by the heat-treatment unit, and the matrix pipe iscompressed and drawn with a constant force into a multi-layer pipehaving a desired diameter by the drawing unit, a high-qualitymulti-layer pipe having improved formability, corrosion resistance, andstrength can be obtained with relatively simple configuration andrelatively low cost.

Further, mechanical bonding of a plurality of pipes including thereceiving pipe and the insert pipe(s) suitable to increase corrosionresistance and strength of the pipes can be obtained with a simpleconfiguration, and at the same time, the receiving pipe and the insertpipe(s) can be metallurgically bonded together through hot forming bythe heat-treatment unit such as the heat furnace or the high-frequencyinduction heater, thereby providing excellent manufacturing efficiencyin situ with low cost.

Further, with the configuration in which the drawing force and theextrusion force are held identically or differently by the drawing unitand the ram, respectively, and respective layers of the multi-layerpipe, i.e. the receiving pipe and the insert pipe(s), which constitutethe matrix pipe, are precisely size-controlled, with the thicknessesthereof maintained to be constant during extrusion using the mandrelwhile clamping the multi-layer pipe by the clamp, thus a multi-layerpipe having improved layer-bonding force and dimension precision can beobtained.

DESCRIPTION OF DRAWINGS

FIG. 1 is an entire configuration of a multi-layer pipe manufacturingapparatus according to an embodiment of the present invention;

FIG. 2 is an enlarged conceptual view of a section A of FIG. 1;

FIG. 3 is a cross-sectional conceptual view illustrating a detailedstructure of a die of a drawing unit, without a matrix pipe and amulti-layer pipe from the section A of FIG. 1;

FIG. 4 is a flow block diagram of a method of manufacturing amulti-layer pipe using the multi-layer pipe manufacturing apparatusaccording to an embodiment of the present invention; and

FIGS. 5 and 6 are perspective views illustrating the structures of areceiving pipe or an insert pipe for a multi-layer pipe to bemanufactured by the multi-layer pipe manufacturing apparatus accordingto an embodiment of the present invention.

DESCRIPTION OF SIGNS

-   -   100 . . . ram    -   200 . . . heat-treatment unit    -   300 . . . drawing unit    -   310 . . . die    -   310 a . . . first side    -   310 b . . . second side    -   310 h . . . extrusion hole section    -   311 . . . first end hole    -   312 . . . second end hole    -   313 a . . . first extrusion guide part    -   313 b . . . second extrusion guide part    -   314 . . . middle hole    -   320 . . . clamp    -   321 . . . chuck    -   330 . . . carrier    -   340 . . . mandrel    -   400 . . . receiving pipe    -   401, 402 . . . reinforcing rib    -   500 . . . insert pipe    -   501, 502 . . . reinforcing rib    -   600 . . . matrix pipe    -   700 . . . multi-layer pipe    -   D1 . . . first diameter    -   D2 . . . second diameter    -   S1 . . . first stage    -   S2 . . . second stage    -   S3 . . . third stage    -   S4 . . . fourth stage

BEST MODE

The advantages and features of the present invention and methodsaccomplishing the same will be apparent when referring to followingembodiments to be described in detail, in conjunction with theaccompanying drawings.

The present invention may not, however, be limited to the embodimentsdisclosed, but be embodied in many different forms.

Here, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the inventionto those skilled in the art to which the present invention pertains.

Therefore, the present invention is only defined by the scope of claims.

Therefore, in some embodiments, well-known components, operations, andtechniques may not be described in detail in order to prevent thepresent invention from being interpreted ambiguously.

The same reference numerals refer to similar elements throughout thedrawings. The terminology used herein is for the purpose of describingparticular embodiments only and is not intended to limit the invention.

As used herein, the singular forms “a”, “an”, and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, or “includes” and/or “including”, when used in thisspecification, specify the presence of stated features, but do notpreclude the presence or addition of one or more other features.

Unless otherwise defined, the meaning of all terms (including technicaland scientific terms) used herein is the same as that commonlyunderstood by one of ordinary skill in the art to which the presentinvention belongs.

It will be further understood that terms, such as those defined incommonly used dictionaries, will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Reference will now be made in greater detail to a preferred embodimentof the invention with reference to the accompanying drawings.

FIG. 1 is an entire configuration of a multi-layer pipe manufacturingapparatus according to an embodiment of the present invention, FIG. 2 isan enlarged conceptual view of a section A of FIG. 1, and FIG. 3 is across-sectional conceptual view illustrating a detailed structure of adie of a drawing unit, without a matrix pipe and a multi-layer pipe fromthe section A of FIG. 1.

As can be seen from the drawings, the present invention includes a ram100, a heat-treatment unit 200, and a drawing unit 300.

The ram 100 extrudes a matrix pipe 600, which is formed by inserting oneor more insert pipes 500 having different diameters into a receivingpipe 400, with a constant compression force (see solid arrow of FIG. 1).

The heat-treatment unit 200 heat-treats and performs hot forming on thematrix pipe 600 extruded from the ram 100 so as to obtain metallurgicalbonding between the receiving pipe 400 and the insert pipe 500, whichconstitute the matrix pipe 600.

The drawing unit 300 draws, with a constant drawing force (see solidarrow of FIG. 1), the matrix pipe 600 passing through the heat-treatmentunit 200 into a multi-layer pipe 700 having a predefined diameter so asto obtain mechanical bonding between the receiving pipe 400 and theinsert pipe 500, which constitute the matrix pipe 600.

Thus, a high-quality multi-layer pipe 700 having improved formability,corrosion resistance, and strength can be obtained with relative simpleconfiguration and relatively low cost.

Further, since mechanical bonding of a plurality of pipes including thereceiving pipe 400 and the insert pipe(s) 500 suitable to increasecorrosion resistance and strength of the pipes can be obtained with asimple configuration, and at the same time, the receiving pipe 400 andthe insert pipe(s) 500 can be metallurgically bonded together throughhot forming by the heat-treatment unit 200 such as the heat furnace orthe high-frequency induction heater, the multi-layer pipe 700 can beformed with low cost.

The present invention can employ the above embodiment and otherembodiments to be described.

A high-quality multi-layer pipe 700 having no surface and mechanicaldefects can be obtained only when the compression force of the ram 100and the drawing force of the drawing unit 300 are substantially the sameor slightly different.

Of course, the compression force of the ram 100 and the drawing force ofthe drawing unit 300 may be the same and may be properly regulateddepending on materials and properties of the receiving pipe 400 and theinsert pipe 500 along with a design of the multi-layer pipe 700 to bemanufactured.

An outer surface of an outermost insert pipe 500 inserted into thereceiving pipe 400 may come into contact with an inner surface of thereceiving pipe 400, and an outer surface of another insert pipe 500inserted into a former-inserted insert pipe 500 inserted into thereceiving pipe 400 may come into contact with an inner surface of theformer-inserted insert pipe 500.

That is, like this, in addition to two layers, i.e. the receiving pipe400 and the insert pipe 500, coming into contact with each other atinner and outer surfaces thereof, respectively, as shown in the drawing,3 layers, 4 layers or more may come into contact with each other so asto form a multi-layer pipe.

Here, the receiving pipe 400 and the insert pipe 500 may be formed ofsame or different material. For example, the receiving pipe 400 and theinsert pipe 500 may comprise an electric resistance welding (ERW) pipeor a seamless pipe so as to form the matrix pipe 600 and the multi-layerpipe 700.

The insertion pipe 500 may be formed of one of stainless steel,aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy,and a combination thereof.

The receiving pipe 400 may be formed of one of carbon steel, cobalt-basealloy steel, aluminum, aluminum alloy, brass, high manganese steel, anda combination thereof.

The heat-treatment unit 200 may be a heat furnace accommodating thematrix pipe 600 extruded from the ram 100, or a high-frequency inductionheater arranged along a direction in which the matrix pipe 600 extrudedfrom the ram is formed. The matrix pipe 600 may be heat-treated andhot-formed at a temperature ranging from 150° C. to 1350° C. by the heatfurnace or the high-frequency induction heater.

Here, when the heat-treatment unit 200 is the high-frequency inductionheater, it may further include a single-frequency generator (not shown)that generates a single frequency for high-frequency induction heatingbonding of the receiving pipe 400 and the insert pipes 500 that areformed of the same material to constitute the matrix pipe 600.

Further, when the heat-treatment unit 200 is the high-frequencyinduction heater, it may further include a multi-frequency generator(not shown) that generates multi-frequency for high-frequency inductionheating bonding of the receiving pipe 400 and the insert pipes 500,respectively, that are respectively formed of different materials toconstitute the matrix pipe 600.

The drawing unit 300 may include a die 310 having an extrusion holesection 310 h through which the multi-layer pipe 700 is extruded fromthe ram 100 into a smaller outer diameter relative to that of the matrixpipe 600, a clamp 320 clamping an end of the multi-layer pipe 700extruded from the die 310, and a carrier 330 carrying the multi-layerpipe 700 with a constant drawing force along a direction of themulti-layer pipe 700 being extruded, wherein the clamp 320 is providedto the carrier 330.

As shown in detail with reference to FIGS. 2 and 3, the extrusion holesection 310 h includes first and second end holes 311 and 312, first andsecond extrusion guide parts 313 a and 313 b, and a middle hole 314.

The first end hole has a first diameter D1 and is disposed on a firstside 310 a of the die 310 so as to face the ram 100.

The middle hole 314 is disposed in the die 310 concentrically with thefirst end hole 311 and has a second diameter D2 smaller than the firstdiameter D1.

The second end hole 312 is disposed on a second side 310 b of the die310 opposite to the first side 310 a, concentrically with the middlehole 314 and has the second diameter D2.

The first extrusion guide part 313 a connects the first end hole 311 andthe middle hole 314 and has a diameter decreasing towards the carrier330.

The second extrusion guide part 313 b connects the middle hole 314 andthe second end hole 312 and has a constant diameter towards the carrier330.

The first diameter D1 corresponds to an outer diameter of the matrixpipe 600 and the second diameter D2 corresponds to an outer diameter ofthe multi-layer pipe 700.

Thus, the matrix pipe 600 coming from the first end hole 311 with aconstant compression force gradually decreases in diameter along thefirst extrusion guide part 313 a, and is formed into a multi-layer pipe700 having a desired second diameter D2 after passing through the middlehole 314, the second extrusion guide part 313 b, and the second end hole312. Then, the multi-layer pipe 700 is drawn and formed while thecarrier 330 is moved, with the multi-layer pipe 700 clamped by the clamp320.

Preferably, the extrusion guide parts 313 a and 313 b may be providedwith a duplex physical vapor deposition (PVD) coating layer or adiamond-like-carbon (DLC) coating layer.

Such coating layers serve to provide a lubrication feature when thematrix pipe 600 is extruded with constant compression force and themulti-layer pipe 700 is drawn with constant drawing force, therebyfacilitating the forming of the multi-layer pipe 700 through carrying inone direction.

Further, according to the present invention, a portion connecting thefirst and second extrusion guide parts 313 a and 313 b from the middlehole 314 may be formed to be round, so that, when the matrix pipe 600 ofthe first diameter D1 shrinks and is formed into the multi-layer pipe700 of the second diameter D2, surface and internal forming defects ofthe multi-layer pipe 700 can be minimized.

While the carrier 330 is illustrated as a wheeled carrier, the presentinvention is not limited thereto.

The clamp 320 may be provided with a plurality of chucks 321 attached tothe carrier 330 and radially arranged so as to be separated from or tocontact an outer surface of the multi-layer pipe 700.

Although not specifically illustrated, the carrier 330 may be applicableto many precisely-displaceable applications and embodiments such as, forexample, an LM guide with a clamp 320, a combination of a rack with aclamp 320 and a pinion in which the pinion can be moved in one directionin a state of being engaged with the rack.

The drawing unit 300 may further include a mandrel 340 extending fromthe carrier 330 towards the ram 100 separately from the clamp 320 anddisposed at the center of the clamp 320 so as to, when inserted into themulti-layer pipe 700, maintain an inner diameter of the multi-layer pipe700 to be constant.

The mandrel 340 may be provided, on an outer surface thereof, with aduplex physical vapor deposition (PVD) coating layer or adiamond-like-carbon (DLC) coating layer.

Such coating layers serve to provide a lubrication feature when thematrix pipe 600 is extruded with constant compression force and themulti-layer pipe 700 is drawn with constant drawing force, therebyfacilitating the forming of the multi-layer pipe 700 while the matrixpipe is carried in one direction.

Although not specifically illustrated, the apparatus of the presentinvention may further include a rotary actuator (not shown) provided inone or both of the ram 100 and the drawing unit 300 and driven to rotatethe extruded matrix pipe 600 or the drawn multi-layer pipe 700 in onedirection.

The rotary actuator serves to facilitate the extrusion of the matrixpipe 600 by the ram 100 and the drawing of the multi-layer pipe 700 bythe drawing unit 300 with less force.

A method of manufacturing a multi-layer pipe using the multi-layerpipe-manufacturing apparatus according to an embodiment of the presentinvention will now be described with reference to FIG. 4.

First, a matrix pipe 600 is formed by inserting one or more insert pipes500 having different diameters into a receiving pipe 400 (a first stageS1).

Next, the matrix pipe 600 is introduced into a ram 100 to extrude thematrix pipe 600 with a constant compression or extrusion force (a secondstage S2).

Then, the matrix pipe 600 extruded from the ram 100 is introduced into aheat-treatment unit 200 to heat-treat the matrix pipe (a third stageS3).

Subsequently, an end of the matrix pipe 600 heat-treated by the heattreatment unit 200 is clamped and the matrix pipe 600 is drawn with aconstant drawing force to form a multi-layer pipe 700 having a desireddiameter, using a drawing unit 300 (a fourth stage S4).

Here, the compression force and the drawing force may be the same andmay be properly regulated depending on materials and properties of thereceiving pipe 400 and the insert pipe 500 along with a design of themulti-layer pipe 700 to be manufactured.

Here, an outer surface of an outermost insert pipe 500 inserted into thereceiving pipe 400 may come into contact with an inner surface of thereceiving pipe 400, and an outer surface of another insert pipe 500inserted into a former-inserted insert pipe 500 inserted into thereceiving pipe 400 may come into contact with an inner surface of theformer-inserted insert pipe 500.

That is, like this, in addition to two layers, i.e. the receiving pipe400 and the insert pipe 500, coming into contact with each other atinner and outer surfaces thereof, respectively, as shown in the drawing,3 layers, 4 layers or more may come into contact with each other so asto form a multi-layer pipe.

Further, in the third stage S3, specifically, the matrix pipe 600extruded by the ram 100 may be heat-treated at a temperature rangingfrom 150° C. to 1350° C. by a heat furnace accommodating the matrix pipeor a high-frequency induction heater arranged along a circumferentialface of the matrix pipe 600.

Thus, according to the present invention, the drawing force of thedrawing unit 300 and the extrusion force of the ram 100 may bemaintained at the same level and may be held differently depending onmaterials of the receiving pipe 400 and the insert pipe 500, and thenthe multi-layer pipe 700 can be drawn and famed by using the mandrel 340while precisely clamping the multi-layer pipe 700 with the clamp 320.

Further, according to the present invention, respective layers of themulti-layer pipe 700, i.e. the receiving pipe 400 and the insert pipe(s)500, which constitute the matrix pipe 600, are preciselysize-controlled, with the thicknesses thereof maintained to be constant,so that a multi-layer pipe 700 having improved layer-bonding force anddimension precision can be obtained.

Thereafter, correction and faceting processes may be additionallyperformed on the manufactured multi-layer pipe 700, and a process ofchecking inner and outer defects of the multi-layer pipe 700 may also beperformed.

In the meantime, in order to increase the longitudinal structuralstrength of the multi-layer pipe 700 in manufacturing the multi-layerpipe 700 using the above-mentioned method, a receiving pipe 400 and aninsert pipe 500 as shown in FIGS. 5 and 6 may be employed.

As shown in FIG. 5, the receiving pipe 400 or the insert pipe 500 may beprovided, on an outer or inner surface thereof, with a plurality ofreinforcing ribs 401 and 501 spaced at regular intervals and linearlyextending along a longitudinal direction of the receiving pipe 400 orthe insert pipe 500, wherein the reinforcing ribs have alternatinglinear ridges and valleys.

Thus, when the left pipe is the insert pipe 500 and the right pipe isthe receiving pipe 400 in FIG. 5, the reinforcing ribs 501 on the outersurface of the insert pipe 500 are meshed with linear valleys betweenthe reinforcing ribs 401 on the inner surface of the receiving pipe 400and then mechanical and metallurgical bonding are performed thereonthereby to form the multi-layer pipe 700 from the matrix pipe 600.

Further, as shown in FIG. 6, the receiving pipe 400 or the insert pipe500 may be provided, on an outer or inner surface thereof, with aplurality of reinforcing ribs 402 and 502 spaced at regular intervalsand involutely extending along a longitudinal direction of the receivingpipe 400 or the insert pipe 500, wherein the reinforcing ribs 402 and502 have alternating involute ridges and valleys.

Thus, when the left pipe is the insert pipe 500 and the right pipe isthe receiving pipe 400 in FIG. 6, the reinforcing ribs 502 on the outersurface of the insert pipe 500 are meshed with linear valleys betweenthe reinforcing ribs 402 on the inner surface of the receiving pipe 400and then mechanical and metallurgical bonding are performed thereonthereby to form the multi-layer pipe 700 from the matrix pipe 600.

Accordingly, the present invention is directed to an apparatus forsimultaneously bonding a plurality of pipes both mechanically andmetallurgically with a relatively simple configuration and process toeconomically manufacture a multi-layer pipe, and a method ofmanufacturing the multi-layer pipe using the same.

Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. An apparatus for manufacturing a multi-layer pipe, the apparatuscomprising: a ram extruding a matrix pipe, which is formed by insertingone or more insert pipes having different diameters into a receivingpipe, with a constant compression force; a heat-treatment unitheat-treating the matrix pipe extruded from the ram; and a drawing unitdrawing, with a constant drawing force, the matrix pipe passing throughthe heat-treatment unit into a multi-layer pipe having a predefineddiameter.
 2. The apparatus according to claim 1, wherein the constantcompression force and the constant drawing force are identical ordifferent.
 3. The apparatus according to claim 1, wherein an outersurface of an outermost insert pipe inserted into the receiving pipecomes into contact with an inner surface of the receiving pipe, and anouter surface of another insert pipe inserted into a former-insertedinsert pipe inserted into the receiving pipe comes into contact with aninner surface of the former-inserted insert pipe.
 4. The apparatusaccording to claim 1, wherein the heat-treatment unit is a heat furnaceaccommodating the matrix pipe extruded from the ram, or a high-frequencyinduction heater arranged along a direction in which the matrix pipeextruded from the ram is formed.
 5. The apparatus according to claim 4,wherein the high-frequency induction heater includes: a single-frequencygenerator for high-frequency induction heating bonding of the receivingpipe and the insert pipes that are formed of the same material toconstitute the matrix pipe; and a multi-frequency generator forhigh-frequency induction heating bonding of the receiving pipe and theinsert pipes, respectively, that are respectively formed of differentmaterials to constitute the matrix pipe.
 6. The apparatus according toclaim 1, wherein the drawing unit includes: a die having an extrusionhole section through which the multi-layer pipe is extruded from the raminto a smaller outer diameter relative to that of the matrix pipe; aclamp clamping an end of the multi-layer pipe extruded from the die; anda carrier carrying the multi-layer pipe with the constant drawing forcealong a direction of the multi-layer pipe being extruded, the clampbeing provided to the carrier.
 7. The apparatus according to claim 6,wherein the extrusion hole section includes: a first end hole having afirst diameter that is disposed on a first side of the die so as to facethe ram; a middle hole disposed in the die concentrically with the firstend hole and having a second diameter smaller than the first diameter; asecond end hole disposed on a second side of the die opposite to thefirst side, concentrically with the middle hole and having the seconddiameter; a first extrusion guide part connecting the first end hole andthe middle hole and having a diameter decreasing towards the carrier;and a second extrusion guide part connecting the middle hole and thesecond end hole and having a constant diameter towards the carrier,wherein the first diameter corresponds to an outer diameter of thematrix pipe and the second diameter corresponds to an outer diameter ofthe multi-layer pipe.
 8. The apparatus according to claim 6, wherein thedrawing unit further includes a mandrel extending from the carriertowards the ram separately from the clamp and disposed at the center ofthe clamp so as to, when inserted into the multi-layer pipe, maintain aninner diameter of the multi-layer pipe to be constant.
 9. The apparatusaccording to claim 6, wherein the clamp is provided with a plurality ofchucks attached to the carrier and radially arranged so as to beseparated from or to contact an outer surface of the multi-layer pipe.10. The apparatus according to claim 1, wherein the receiving pipe andthe insert pipes are formed of the same material or different materials.11. The apparatus according to claim 1, wherein the receiving pipe andthe insert pipes are any one of an electric resistance welding (ERW)pipe and a seamless pipe.
 12. The apparatus according to claim 1,wherein the insertion pipe is formed of one of stainless steel,aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy,and a combination thereof.
 13. The apparatus according to claim 1,wherein the receiving pipe is formed of one of carbon steel, cobalt-basealloy steel, aluminum, aluminum alloy, brass, high manganese steel, anda combination thereof.
 14. The apparatus according to claim 1, whereinthe receiving pipe or the insert pipe is provided, on an outer or innersurface thereof, with a plurality of reinforcing ribs spaced at regularintervals and linearly extending along a longitudinal direction of thereceiving pipe or the insert pipe, the reinforcing ribs havingalternating linear ridges and valleys.
 15. The apparatus according toclaim 1, wherein the receiving pipe or the insert pipe is provided, onan outer or inner surface thereof, with a plurality of reinforcing ribsspaced at regular intervals and involutely extending along alongitudinal direction of the receiving pipe or the insert pipe, thereinforcing ribs having alternating involute ridges and valleys.
 16. Theapparatus according to claim 1, further comprising a rotary actuatorprovided in one or both of the ram and the drawing unit and driven torotate the extruded matrix pipe or the drawn multi-layer pipe in onedirection.
 17. The apparatus according to claim 6, wherein the extrusionguide parts are provided with a duplex physical vapor deposition (PVD)coating layer or a diamond-like-carbon (DLC) coating layer.
 18. Theapparatus according to claim 8, wherein the mandrel is provided, on anouter surface thereof, with a duplex physical vapor deposition (PVD)coating layer or a diamond-like-carbon (DLC) coating layer.
 19. A methodof manufacturing a multi-layer pipe using an apparatus for manufacturinga multi-layer pipe, the method comprising: a first stage of forming amatrix pipe by inserting one or more insert pipes having differentdiameters into a receiving pipe; a second stage of introducing thematrix pipe into a ram to extrude the matrix pipe with a constantcompression or extrusion force; a third stage of introducing the matrixpipe extruded from the ram into a heat-treatment unit to heat-treat thematrix pipe; and a fourth stage of clamping an end of the matrix pipeheat-treated by the heat treatment unit and drawing the matrix pipe witha constant drawing force to form a multi-layer pipe having a desireddiameter, using a drawing unit.
 20. The method according to claim 19,wherein an outer surface of an outermost insert pipe inserted into thereceiving pipe comes into contact with an inner surface of the receivingpipe, and an outer surface of another insert pipe inserted into aformer-inserted insert pipe inserted into the receiving pipe comes intocontact with an inner surface of the former-inserted insert pipe. 21.The method according to claim 19, wherein in the third stage, the matrixpipe extruded by the ram is heat-treated at a temperature ranging from150° C. to 1350° C. by a heat furnace accommodating the matrix pipe or ahigh-frequency induction heater arranged along a circumferential face ofthe matrix pipe.